As shown in Fig. REF , we consider a two-dimensional UAV-enabled industrial automation scenario, where the UAV hovers at a location \((x,H)\)  above the horizontal line with height \(H\) . The locations of the controller and the robot are \((0,0)\)  and \((D,0)\) . The packet size of the command information is \(L\)  bits, which should be completed within \(T_{\rm {max}}\)  seconds. Then, the overall blocklength is given by \(M=BT_{\rm {max}}\)  [1]}, where \(B\)  is system bandwidth. The total transmission has two phases, i.e., the first one corresponds to the transmission from the controller to the UAV, while the second one is the transmission from the UAV to the robot. We assume that the UAV adopts the AF protocol, which simply amplifies and forwards the received signals to the robot. Hence, the blocklength for these two phases should be equal, e.g., \(m_1=m_2=m\triangleq M/2\) . The transmit power of the controller and the UAV are respectively \(p_1\)  and \(p_2\) .
